Measles encephalomyelitis--clinical and immunologic studies

Measles - Resurgence of an Old Foe

Measles was a leading cause of childhood morbidity and mortality before introduction of an extremely effective vaccine. Incidence dropped dramatically, but has increased recently given incomplete vaccination coverage and high levels of contagion. Clinicians must have a high index of suspicion for measles when evaluating febrile viral exanthems in susceptible hosts. Diagnosis can be made with serum immunoglobulin M or polymerase chain reaction. Treatment with vitamin A is recommended in children with severe measles. Vaccination with 2 doses of vaccine is the mainstay of prevention and 95% coverage is required for herd immunity.

What's going on with measles?

Measles is a highly transmissible systemic viral infection associated with substantial mortality primarily due to secondary infections. Measles induces lifelong immunity to reinfection but loss of immunity to other pathogens. An attenuated live virus vaccine is highly effective, but lapses in delivery have resulted in increasing cases worldwide. Although the primary cause of failure to control measles is failure to vaccinate, waning vaccine-induced immunity and the possible emergence of more virulent virus strains may also contribute.

Rubella virus chronic inflammatory disease and other unusual viral phenotypes in inborn errors of immunity

Infectious susceptibility is a component of many inborn errors of immunity. Nevertheless, antibiotic use is often used as a surrogate in history taking for infectious susceptibility, thereby disadvantaging patients who present with viral infections as their phenotype. Further complicating clinical evaluations are unusual manifestations of viral infections which may be less familiar that the typical respiratory viral infections. This review covers several unusual viral phenotypes arising in patients with inborn errors of immunity and other settings of immune compromise. In some cases, chronic infections lead to oncogenesis or tumor-like growths and the conditions and mechanisms of viral-induced oncogenesis will be described. This review covers enterovirus, rubella, measles, papillomavirus, and parvovirus B19. It does not cover EBV and hemophagocytic lymphohistiocytosis nor lymphomagenesis related to EBV. EBV susceptibility has been recently reviewed. Our goal is to increase awareness of the unusual manifestations of viral infections in patients with IEI and to describe treatment modalities utilized in this setting. Coincidentally, each of the discussed viral infections can have a cutaneous component and figures will serve as a reminder of the physical features of these viruses. Given the high morbidity and mortality, early recognition can only improve outcomes.

Measles-Associated CNS Complications: A Review

Measles virus infection is a common infectious disease of childhood, incidence of which is still high in developing countries. Other than the morbidity associated with the acute systemic infection, the measles virus can cause serious fatal neural complications. It can either enter the brain leading to acute encephalitis like primary measles encephalitis and acute post infectious measles encephalomyelitis or it may persist in brain cells (as mutated virus) leading to long-term neurodegenerative diseases like measles inclusion body encephalitis and subacute sclerosing pan encephalitis. The patho-clinical features, treatment, and the outcomes of these complications are different and should be identified in time for early diagnosis and management.

Measles immunity and immunosuppression

Effects of measles on the immune system are only partially understood. Lymphoid tissue is a primary site of measles virus (MeV) replication where CD150 is the receptor for infection of both B and T cells. Lymphocyte depletion occurs during the acute phase of infection, but initiation of the adaptive immune response leads to extensive lymphocyte proliferation, production of MeV-specific antibody and T cells, the rash and clearance of infectious virus. Viral RNA persists in lymphoid tissue accompanied by ongoing germinal center proliferation, production of antibody-secreting cells, functionally distinct populations of T cells and antibody avidity maturation to establish life-long immunity. However, at the same time diversity of pre-existing antibodies and numbers of memory and naive B cells are reduced and susceptibility to other infections is increased.

Adverse events associated with Measles and Rubella vaccination campaign 2019 in India

Purpose

The purpose of this study is to study the various adverse reactions caused post measles and rubella vaccination done during measles rubella (MR) vaccine campaign in India.

Materials and Methods

Prospective, observational study was done in a government tertiary care pediatric intensive care unit. Children aged between 9 months to 15 years, who presented with adverse effects (severe enough to warrant admission) within 7 days of MR vaccine administration.

Results

Most common presenting complaint was fever (44.8%), followed by vomiting (34.5%), abdominal pain and dizziness (31%). Abnormal body movements were noted in two children (6.8%) on first day and in one child on fifth day of vaccine administration. Two children (6.8%) presented with generalized macular rashes all over the body on 4th day after vaccination. Altered sensorium on same day of vaccine administration was the presenting symptom of one child. All children improved gradually and were discharged after few days with no mortality or long-term morbidity. Investigations were done according to the protocol of the unit; nothing came significant to be reported. Neither of the children had positive blood culture.

Conclusion

MR vaccination programs are scientifically sound, highly recommended and proven effective globally. Causality assessment of adverse events is still an evolving science, and despite taking all the measures and adopting all the available scientific methods, sometimes it is not possible to incontrovertibly prove the causal association of an event with a vaccine. Much more advancement in this area is needed.

A Rewarding Career Unraveling the Pathogenesis of Viral Infections

My great-grandparents were immigrants from Sweden and settled as farmers in Iowa and Illinois. My father, the oldest of six children, was the first in his family to go to college and had careers as a petroleum geologist and an academic. My mother, the youngest of four children, had older siblings in education, and she focused on early childhood education. My childhood in Oklahoma with two younger sisters was happy and comfortable, and public school prepared me well. My career trajectory into virology did not involve much if any advance planning but was characterized by recognizing the fascinating puzzles of virus diseases, being in good places at the right time, taking advantage of opportunities as they presented themselves, and being surrounded by great mentors, colleagues, trainees, and family. Most of my career was spent studying two diseases caused by RNA viruses, alphavirus encephalomyelitis and measles, and was enriched with several leadership opportunities.

Measles virus persistence and its consequences

Clearance of measles virus is complex. Infectious virus is cleared by the adaptive immune response manifested by the characteristic maculopapular rash. CD8+ T cells are major effectors of infectious virus clearance, a process that may fail in individuals with compromised cellular immune responses leading to progressive giant cell pneumonia and/or measles inclusion body encephalitis. In contrast to the usual rapid clearance of infectious virus, clearance of viral RNA is slow with persistence in lymphoid tissue for many months. Persistence of MeV RNA may contribute to the late development of the slowly progressive disease subacute sclerosing panencephalitis in children infected at a young age and to measles-associated immune suppression but also to maturation of the immune response and development of life-long immunity.

Complications of measles: a case series

Measles, which was once thought to be a disappearing viral infection due to effective vaccination, has been re-emerging globally, with increasing cases in adolescents and adults. This has been attributed to anti-vaccination campaigning in the early 21st century, which has resulted in a drop in overall herd immunity. In this case series we report three patients with complications secondary to measles who presented to a hospital in Malta in 2019. Through this series, we discuss the range of possible complications caused by the measles virus, ranging from mild viraemic symptoms to multiorgan involvement which could possibly lead to high-dependency care and may even be fatal. We also highlight recent global statistics which reflect the exponential increase in the incidence of measles, with a special focus on Europe. It is emphasised that vaccine education and compliance with the two-dose measles vaccine should be implemented worldwide.

Neurological Complications of Measles (Rubeola)

PURPOSE OF REVIEW

Owing to vaccine hesitancy, there has been a resurgence of measles infections in developed countries. Practitioners can expect to see an increase in patients with neurologic complications of measles. These devastating disorders include primary measles encephalitis, acute post measles encephalitis, subacute sclerosing panencephalitis (SSPE), and measles inclusion body encephalitis (MIBE).

RECENT FINDINGS

Although there are many unanswered questions regarding the neurologic complications of measles, recent advances have led to better understanding of the mechanism of the spread of measles within the nervous system, particularly the disruption of F protein function, which raises the possibility of treatment with fusion-inhibiting molecules. Measles and its neurological complications are preventable and must be prevented. Neurologists must educate other clinicians and the public regarding the consequences of inadequate herd immunity to measles. More effective treatments for SSPE and MIBE may be available in the near future, but currently these remain lethal diseases.

Measles Encephalitis: Towards New Therapeutics

Measles remains a major cause of morbidity and mortality worldwide among vaccine preventable diseases. Recent decline in vaccination coverage resulted in re-emergence of measles outbreaks. Measles virus (MeV) infection causes an acute systemic disease, associated in certain cases with central nervous system (CNS) infection leading to lethal neurological disease. Early following MeV infection some patients develop acute post-infectious measles encephalitis (APME), which is not associated with direct infection of the brain. MeV can also infect the CNS and cause sub-acute sclerosing panencephalitis (SSPE) in immunocompetent people or measles inclusion-body encephalitis (MIBE) in immunocompromised patients. To date, cellular and molecular mechanisms governing CNS invasion are still poorly understood. Moreover, the known MeV entry receptors are not expressed in the CNS and how MeV enters and spreads in the brain is not fully understood. Different antiviral treatments have been tested and validated in vitro, ex vivo and in vivo, mainly in small animal models. Most treatments have high efficacy at preventing infection but their effectiveness after CNS manifestations remains to be evaluated. This review describes MeV neural infection and current most advanced therapeutic approaches potentially applicable to treat MeV CNS infection.

Measles-related hospitalizations and associated complications in Jerusalem, 2018-2019

OBJECTIVES

The 2018 measles outbreak in Israel affected >2000 people in Jerusalem. The aim of the study was to describe clinical features and complications of hospitalized measles patients in Jerusalem, as related to age group and risk factors.

METHODS

All individuals hospitalized with measles in the three main hospitals in Jerusalem during March 2018 to February 2019 were included. Demographic, clinical and laboratory data were analysed.

RESULTS

Of 161 hospitalized individuals, 86 (53.4%) were <5 years old, 16 (10%) were ≥5 years but <20 years old, and 59 (36.6%) were ≥20 years old. Most, 114/135 (85%), were unvaccinated. Immunocompromised state was identified in 12/161 (7.5%) patients, 20/161 (12.4%) had other underlying co-morbidities, and four were pregnant. Hypoxaemia on admission was a common finding in all age groups. Hepatitis was more common among adults ≥20 years old (33/59, 59%). Measles-related complications were noted in 95/161 (59%) patients, and included pneumonia/pneumonitis (67/161, 41.6%), which was more common in young (<5 years) children, diarrhoea (18/161, 11.2%), otitis (18/161, 11.2%), and neurological complications (6/161, 3.7%)-the latter occurring more frequently in the 5- to 20-year age group. Two of the 12 immunocompromised patients died of measles-related complications. A high re-admission rate (19/161, 11.8%) within 3 months was documented among hospitalized measles patients.

CONCLUSION

The burden of hospitalization, as well as the high rate of short- and long-term complications observed in hospitalized patients, underscore the importance of maintaining a high measles vaccine coverage, with enhanced targeting of unvaccinated population pockets.

Measles Vaccine

Measles remains an important cause of child morbidity and mortality worldwide despite the availability of a safe and efficacious vaccine. The current measles virus (MeV) vaccine was developed empirically by attenuation of wild-type (WT) MeV by in vitro passage in human and chicken cells and licensed in 1963. Additional passages led to further attenuation and the successful vaccine strains in widespread use today. Attenuation is associated with decreased replication in lymphoid tissue, but the molecular basis for this restriction has not been identified. The immune response is age dependent, inhibited by maternal antibody (Ab) and involves induction of both Ab and T cell responses that resemble the responses to WT MeV infection, but are lower in magnitude. Protective immunity is correlated with levels of neutralizing Ab, but the actual immunologic determinants of protection are not known. Because measles is highly transmissible, control requires high levels of population immunity. Delivery of the two doses of vaccine needed to achieve >90% immunity is accomplished by routine immunization of infants at 9-15 months of age followed by a second dose delivered before school entry or by periodic mass vaccination campaigns. Because delivery by injection creates hurdles to sustained high coverage, there are efforts to deliver MeV vaccine by inhalation. In addition, the safety record for the vaccine combined with advances in reverse genetics for negative strand viruses has expanded proposed uses for recombinant versions of measles vaccine as vectors for immunization against other infections and as oncolytic agents for a variety of tumors.

Neurologic autoimmunity: mechanisms revealed by animal models

Over the last decade, neurologic autoimmunity has become a major consideration in the diagnosis and management of patients with many neurologic presentations. The nature of the associated antibodies and their targets has led to appreciation of the importance of the accessibility of the target antigen to antibodies, and a partial understanding of the different mechanisms that can follow antibody binding. This chapter will first describe the basic principles of autoimmune inflammation and tissue damage in the central and peripheral nervous system, and will then demonstrate what has been learnt about neurologic autoimmunity from circumstantial clinical evidence and from passive, active, and occasionally spontaneous or genetic animal models. It will cover neurologic autoimmune diseases ranging from disorders of neuromuscular transmission, peripheral and ganglionic neuropathy, to diseases of the central nervous system, where autoantibodies are either pathogenic and cause destruction or changes in function of their targets, where they are harmless bystanders of T-cell-mediated tissue damage, or are not involved at all. Finally, this chapter will summarize the relevance of current animal models for studying the different neurologic autoimmune diseases, and it will identify aspects where future animal models need to be improved to better reflect the disease reality experienced by affected patients, e.g., the chronicity or the relapsing/remitting nature of their disease.

Acute disseminated encephalomyelitis: current knowledge and open questions

Acute disseminated encephalomyelitis (ADEM) is usually an acute, multi-focal, and monophasic immune-mediated disease of the central nervous system. The disorder is mainly a condition of the pediatric age group, but neurologists are also involved in the management of adult patients. The lack of defined diagnostic criteria for ADEM underlies the limited understanding of its epidemiology, etiology, pathogenesis, course, prognosis, therapy, as well as the association with, and distinction from, multiple sclerosis. The present review summarizes current knowledge and outlines unanswered questions the answers to which should be eventually provided through a synergistic combination of clinical and basic research.

[An update on measles]

Measles is a highly contagious infectious disease, which needs more than 95% worldwide vaccination coverage of 2 doses to be eradicated. Despite an important involvement of the WHO for massive immunization, goals have not bean reached, and outbreaks can occur at any time in many countries, including Western Europe. In France, 22,000 cases were identified between 2009 and 2011, mainly in infants and young adults, which are not or not enough vaccinated (one dose). In 2012, even though the number of cases has drastically decreased, the outbreak is still going on, especially in South of France. That is why every clinician needs to be concerned about the clinical manifestations of the disease, and its complications. Besides a febrile rash, measles is often responsible of pneumonia and biologic hepatitis in adults. Hepatitis does not seem frequent in children. Clinicians need to be aware of specific complications, like encephalitis in case of cellular immunodepression, high risk of pneumonia in pregnant women. In patients previously vaccinated, incidence of complications is the same but patients are not contagious. Even if measles diagnosis is clinical, blood confirmation by serology is recommended in France when possible. Outcome is mainly favourable, but measles is not well-tolerated with high levels of hospitalisation even without any complication. Vaccination is the only way to protect against it.

Subacute Sclerosing Panencephalitis Presenting with Unilateral Periodic Myoclonic Jerks

Background:

Subacute sclerosing panencephalitis (SSPE) is a rare complication of measles virus infection. The disease is characterized by behavioural abnormalities, intellectual deterioration, motor weakness, and generalized myoclonic jerks progressing to coma and death in one to two years in 80% of the cases. The myoclonic jerks are associated with characteristic generalized slow periodic complexes on electroencephalography (EEG). The symptoms and signs of SSPE are frequently quite variable. The clinical course is equally variable and difficult to predict. The characteristic periodic myoclonus can rarely occur unilaterally particularly in the early stages of the disease. As well, the periodic EEG complexes have been reported unilaterally in up to 3% of cases.

Case Report:

A 12-year-old boy, who was seen at a later stage with atypical manifestation of myoclonic body jerks confined entirely unilaterally, combined with contralateral periodic EEG complexes. One could assume clinically that the more diseased hemisphere was responsible for generating the jerks. However, brain magnetic resonance imaging revealed asymmetric hemispheric changes suggesting that the less neurologically damaged hemisphere is responsible for generating the unilateral myoclonic jerks. This has led to the interpretation that the more severely damaged hemisphere has lost the neuronal connectivity required to generate these periodic myoclonic jerks.

Conclusion:

Subacute sclerosing panencephalitis may have asymmetric hemispheric involvement, not only early, but also in the advanced stages of the disease, which can result in unilateral periodic myoclonic jerks.

Measles, mumps, rubella, and human parvovirus B19 infections and neurologic disease

While the systemic disorders associated with measles, mumps, and rubella viruses and human parvovirus B19 tend to be mild, each virus can produce potentially life-threatening neurologic disease in human hosts, especially when these viruses infect young children. Two of the viruses, rubella and parvovirus B19, can be vertically transmitted to fetuses during maternal infection and cause congenital infection. Neurologic complications are common after intrauterine infection with the rubella virus, a condition known as the congenital rubella syndrome. Two, measles and rubella viruses, can induce "slow viral" infections, serious, disorders that can occur several years after the initial exposure to the virus and typically have fatal outcomes.

Infections and multiple sclerosis

Multiple sclerosis is a chronic inflammatory condition of unknown cause. Increasing evidence suggests that the disease develops as a result of interactions between the environment and the immune system in genetically susceptible individuals. It has long been recognized that infections may serve as environmental triggers for the disease, and a large number of pathogens have been proposed to be associated with multiple sclerosis. Here, we detail the historical basis linking infections to multiple sclerosis and review the epidemiology of the disease, which suggests a possible relationship with infectious agents. We also describe pathophysiologic studies in animals and other human demyelinating diseases that have demonstrated a variety of mechanisms by which infectious agents may induce chronic, relapsing central nervous system disease with myelin damage and relative preservation of axons, similar to multiple sclerosis. In addition, we discuss recent studies in individuals with multiple sclerosis indicating enhanced immune responses to infectious antigens, though not consistently demonstrating evidence for ongoing infection. Taken together, these studies suggest a role for infectious agents in the development of multiple sclerosis. Conclusive evidence, however, remains lacking.

Severe Measles Infection: The Spectrum of Disease in 36 Critically Ill Adult Patients

France has recently witnessed a nationwide outbreak of measles. Data on severe forms of measles in adults are lacking. We sought to describe the epidemiologic, clinical, treatment, and prognostic aspects of the disease in adult patients who required admission to an intensive care unit (ICU). We performed a retrospective analysis of a cohort of 36 adults admitted to a total of 64 ICUs throughout France for complications of measles from January 1, 2009, to December 31, 2011. All cases of measles were confirmed by serologic testing and/or reverse transcription polymerase chain reaction.The cohort consisted of 21 male and 15 female patients, with a median age of 29.2 years (25th-75th interquartile range [IQR], 27.2-34.2 yr) and a median Simplified Acute Physiology Score (SAPS II) of 13 (IQR, 9-18). Among the 26 patients whose measles vaccination status was documented, none had received 2 injections. One patient had developed measles during childhood. Underlying comorbid conditions included chronic respiratory disease in 9 patients, immunosuppression in 7 patients, and obesity in 3 patients, while measles affected 5 pregnant women.Respiratory complications induced by measles infection led to ICU admission in 32 cases, and measles-related neurologic complications led to ICU admission in 2 cases. Two patients were admitted due to concurrent respiratory and neurologic complications.Bacterial superinfection of measles-related airway infection was suspected in 28 patients and was documented in 8. Four cases of community-acquired pneumonia, 6 cases of ventilator-associated pneumonia, 1 case of tracheobronchitis, and 2 cases of sinusitis were microbiologically substantiated.Of 11 patients who required mechanical ventilation, 9 developed acute respiratory distress syndrome (ARDS). Among the patients with ARDS, extraalveolar air leak complications occurred in 4 cases. Five patients died, all of whom were severely immunocompromised.On follow-up, 1 patient had severe chronic respiratory failure related to lung fibrosis, and 2 patients had mild lower limb paraparesis along with bladder dysfunction, both of which were ascribable to measles-induced encephalitis and myelitis. Among the 5 pregnant patients, the course of measles infection was uneventful, albeit 1 patient underwent emergent cesarean delivery because of fetal growth restriction.Measles is a disease with protean and potentially deceptive clinical manifestations, especially in the immunocompromised patient. Measles-associated pneumonitis and its complications, and less commonly postinfectious encephalomyelitis, are the main source of morbidity and mortality. In contrast with the usually benign course of the disease in immunocompetent patients, measles occurring in immunocompromised patients gives rise to lethal complications including ARDS, with or without bacterial superinfection. Other patients potentially at high risk for severe measles are young adults and pregnant women. Measles pneumonitis may predispose to air leak disease in patients using mechanical ventilation. To date, vaccination remains the most potent tool to control measles infection.

Acute measles encephalitis in partially vaccinated adults

BACKGROUND

The pathogenesis of acute measles encephalitis (AME) is poorly understood. Treatment with immune-modulators is based on theories that post-infectious autoimmune responses cause demyelination. The clinical course and immunological parameters of AME were examined during an outbreak in Vietnam.

METHODS AND FINDINGS

Fifteen measles IgM-positive patients with confusion or Glasgow Coma Scale (GCS) score below 13, and thirteen with uncomplicated measles were enrolled from 2008-2010. Standardized clinical exams were performed and blood collected for lymphocyte and measles- and auto-antibody analysis. The median age of AME patients was 21 years, similar to controls. Eleven reported receiving measles vaccination when aged one year. Confusion developed a median of 4 days after rash. Six patients had GCS <8 and four required mechanical ventilation. CSF showed pleocytosis (64%) and proteinorrhachia (71%) but measles virus RNA was not detected. MRI revealed bilateral lesions in the cerebellum and brain stem in some patients. Most received dexamethasone +/- IVIG within 4 days of admission but symptoms persisted for ≥3 weeks in five. The concentration of voltage gated calcium channel-complex-reactive antibodies was 900 pM in one patient, and declined to 609 pM ∼ 3 months later. Measles-reactive IgG antibody avidity was high in AME patients born after vaccine coverage exceeded 50% (∼ 25 years earlier). AME patients had low CD4 (218/µl, p = 0.029) and CD8 (200/µl, p = 0.012) T-cell counts compared to controls.

CONCLUSION

Young adults presenting with AME in Vietnam reported a history of one prior measles immunization, and those aged <25 years had high measles-reactive IgG avidity indicative of prior vaccination. This suggests that one-dose measles immunization is not sufficient to prevent AME in young adults and reinforces the importance of maintaining high coverage with a two-dose measles immunization schedule. Treatment with corticosteroids and IVIG is common practice, and should be assessed in randomized clinical trials.

Pediatric Inflammatory Diseases. Part II: Acute Post-Infectious Immune Disorders

Acute post-infectious immune disorders include Acute Disseminated Encephalomyelitis (ADEM) and its variants such as Acute Hemorrhagic Encephalomyelitis (AHEM), acute necrotizing hemorrhagic leukoencephalitis (ANHLE) of Weston Hurst, multiphasic and recurrent ADEM. Acute Necrotizing Encephalopathy of Childhood (ANE or ANEC) represents a dramatic event, consequent to viral infections, especially Influenza-A, and is now considered different from ADEM. ADEM and variants are classically described as uniphasic syndrome occurring in association with an immunization or vaccination (postvaccine encephalomyelitis) or systemic viral infection (parainfectious encephalomyelitis). However, multiphasic forms are not rare. Pathologically, there is perivascular inflammation, edema, and demyelination within the CNS. Clinical features are focal or multifocal neurologic disorder following exposure to virus or receipt of vaccine. The onset of the CNS disorder is usually rapid and include encephalopathy ranging from lethargy to coma, seizures, and focal and multifocal signs reflecting cerebral and spinal cord involvement. The mortality rate is estimated at 10 to 30 percent, with complete recovery rates of 50 percent cited. Poor prognosis is correlated with severity and abruptness of onset of the clinical syndrome. Multifocal CNS lesions are generally evident on MRI that can be similar from those observed in MS.

Immature CD4+CD8+ thymocytes are preferentially infected by measles virus in human thymic organ cultures

Cells of the human immune system are important target cells for measles virus (MeV) infection and infection of these cells may contribute to the immunologic abnormalities and immune suppression that characterize measles. The thymus is the site for production of naïve T lymphocytes and is infected during measles. To determine which populations of thymocytes are susceptible to MeV infection and whether strains of MeV differ in their ability to infect thymocytes, we used ex vivo human thymus organ cultures to assess the relative susceptibility of different subpopulations of thymocytes to infection with wild type and vaccine strains of MeV. Thymocytes were susceptible to MeV infection with the most replication in immature CD4⁺CD8⁺ double positive cells. Susceptibility correlated with the level of expression of the MeV receptor CD150. Wild type strains of MeV infected thymocytes more efficiently than the Edmonston vaccine strain. Thymus cultures from children ≥3 years of age were less susceptible to MeV infection than cultures from children 5 to 15 months of age. Resistance in one 7 year-old child was associated with production of interferon-gamma suggesting that vaccination may result in MeV-specific memory T cells in the thymus. We conclude that immature thymocytes are susceptible to MeV infection and thymocyte infection may contribute to the immunologic abnormalities associated with measles.

Measles virus and associated central nervous system sequelae

Worldwide, measles remains one of the most deadly vaccine-preventable diseases. In the United States, enrollment in the public schools requires that each child receives 2 doses of measles-containing vaccine before entry, essentially eliminating this once endemic disease. Recent outbreaks of measles in the United States have been associated with importation of measles virus from other countries and subsequent transmission to intentionally undervaccinated children. The central nervous system complications of measles can occur within days or years of acute infection and are often severe. These include primary measles encephalitis, acute postinfectious measles encephalomyelitis, measles inclusion body encephalitis, and subacute sclerosing panencephalitis. These measles-associated central nervous system diseases differ in their pathogenesis and pathologic effects. However, all involve complex brain-virus-immune system interactions, and all can lead to severe and permanent brain injury. Despite better understanding of the clinical presentations and pathogenesis of these illnesses, effective treatments remain elusive.

Molecular mimicry as a mechanism of autoimmune disease

A variety of mechanisms have been suggested as the means by which infections can initiate and/or exacerbate autoimmune diseases. One mechanism is molecular mimicry, where a foreign antigen shares sequence or structural similarities with self-antigens. Molecular mimicry has typically been characterized on an antibody or T cell level. However, structural relatedness between pathogen and self does not account for T cell activation in a number of autoimmune diseases. A proposed mechanism that could have been misinterpreted for molecular mimicry is the expression of dual T cell receptors (TCR) on a single T cell. These T cells have dual reactivity to both foreign and self-antigens leaving the host vulnerable to foreign insults capable of triggering an autoimmune response. In this review, we briefly discuss what is known about molecular mimicry followed by a discussion of the current understanding of dual TCRs. Finally, we discuss three mechanisms, including molecular mimicry, dual TCRs, and chimeric TCRs, by which dual reactivity of the T cell may play a role in autoimmune diseases.

Measles

Measles is a highly contagious disease caused by measles virus and is one of the most devastating infectious diseases of man--measles was responsible for millions of deaths annually worldwide before the introduction of the measles vaccines. Remarkable progress in reducing the number of people dying from measles has been made through measles vaccination, with an estimated 164,000 deaths attributed to measles in 2008. This achievement attests to the enormous importance of measles vaccination to public health. However, this progress is threatened by failure to maintain high levels of measles vaccine coverage. Recent measles outbreaks in sub-Saharan Africa, Europe, and the USA show the ease with which measles virus can re-enter communities if high levels of population immunity are not sustained. The major challenges for continued measles control and eventual eradication will be logistical, financial, and the garnering of sufficient political will. These challenges need to be met to ensure that future generations of children do not die of measles.

Acute disseminated encephalomyelitis preceding measles exanthema

We report a case of acute disseminated encephalomyelitis preceding measles virus infection. Brain magnetic resonance imaging revealed signal intensity abnormalities in the basal ganglia and cortex consistent with acute disseminated encephalomyelitis. Fever and the first Koplik spots appeared 8 and 10 days later, respectively. This case supports the hypothesis that the immune-mediated demyelinating process may occur before the symptomatic phase of a viral infection. Therefore, children without history of infectious disorders should also have acute disseminated encephalomyelitis included in the differential considerations.

Metagenomics and the molecular identification of novel viruses

There have been rapid recent developments in establishing methods for identifying and characterising viruses associated with animal and human diseases. These methodologies, commonly based on hybridisation or PCR techniques, are combined with advanced sequencing techniques termed ‘next generation sequencing’. Allied advances in data analysis, including the use of computational transcriptome subtraction, have also impacted the field of viral pathogen discovery. This review details these molecular detection techniques, discusses their application in viral discovery, and provides an overview of some of the novel viruses discovered. The problems encountered in attributing disease causality to a newly identified virus are also considered.

Measles Outbreak in Qatar 2007

To analyze the epidemiological and clinical characteristic of a measles outbreak in Qatar in 2007, the records of 21 2 confirmed cases of measles were analyzed retrospectively, confirmation being based on clinical suspicion of the disease with a positive measles IgM (170 cases) and /or exposure to a laboratory confirmed measles case during the infectious period (42 cases; epidemiologic link). Eighty five percent of the cases occurred between April and July. Seventeen percent were in infants <  1 year of age, 47% in children between 1-5 years of age, 24% in school age children < 10 year of age and 1 2% in children >10 years old. Vaccinations were up to date in 60% of cases, second dose missed in 30% and no vaccination in 10% because of travel outside the country, concurrent illness, or lack of transportation. Thirty one percent of the cases required admission, with a mean hospital stay of four days. Cases were reported predominantly in Pakistani and Qatari patients, living mainly in three areas within the capital, Abu Hammour, Al Rayyan, and Al Mamuora.

Conclusion: Status of vaccination in Qatar needs careful analysis and the vaccination schedule should be reviewed. Early administration of vaccine, increasing community awareness, a well-coordinated school-based immunization program and immunization campaigns are required to prevent future outbreaks.

Neurologic and muscular complications of the 2009 influenza A (H1N1) pandemic

In the spring of 2009 a new triple-reassortant of influenza A (H1N1) virus appeared in Mexico and rapidly spread around the world, becoming a pandemic that primarily infected children and uncommonly older adults. Accompanying the pandemic were associated neurologic and muscular syndromes that affected primarily children and included febrile seizures, encephalopathy/encephalitis with or without seizures, delirium, focal neurologic syndromes, Guillain-Barré syndrome, myositis, and myocarditis. Neither the frequency nor the severity of these syndromes appears different from those recognized during periods of infections of previous influenza A viruses. I review the clinical, laboratory, neuroimaging, and pathologic characteristics of the associated syndromes appearing in the first wave of the pandemic, compare them to similar cases occurring in previous years, and explore several theories of pathogenesis.